In the field of vehicle drivetrain components, a transfer case is an apparatus that distributes driving power to more than one driven axle of the vehicle. A typical transfer case receives driving power from the transmission of the vehicle and transfers that power to a primary output shaft that is driven constantly, for example, during operation of the vehicle in a two-wheel drive mode, and a secondary output shaft that is driven selectively using a clutch, for example, during operation of the vehicle in a four-wheel drive mode. In addition, two-speed transfer cases may provide gear reduction to allow operation in a high range, which is typically a 1:1 drive ratio, or a low range, such as a 2:1 drive ratio.
Many of the components in a transfer case, including the clutch, require lubrication. One transfer case design includes a pump that may be mounted on either the input shaft or the primary output shaft. The pump delivers lubricant to the various components of the transfer case through an axial bore that is formed through the input shaft and/or the output shafts. Supply ports are formed through the input shaft and/or the output shafts at locations where lubrication is needed, such that the lubricant flows from the pump, through the axial bore, and out of the supply ports. This arrangement is effective, but offers little control over delivery of lubricant, for example, to the clutch that has variable lubrication needs depending on the mode and range of vehicle operation.